The present invention relates to a printing and reproducing machine, and more particularly, to a security system for ensuring that cartridges are being used within their effective lifespan and according to any existing warranty or license.
Printing and reproducing machines, such as electrostatographic and inkjet printers and copiers, commonly employ one or more replaceable sub-assemblies or units, generally referred to as cartridges or CRU""s (Customer Replaceable Units). A common replaceable cartridge, or CRU, is the photoreceptor cartridge containing the photoreceptor and necessary supporting hardware in a single unit designed for insertion and removal into and out of the machine. When a cartridge is expended, the old cartridge is removed and a new cartridge is installed. Other frequently used replaceable cartridges include developer cartridges, toner cartridges, ink cartridges or tanks, and developer replenisher bottles.
U.S. Pat. No. 4,585,327 (Suzuki) discloses a copier employing a removable magazine containing a photosensitive belt. A counter in the machine""s controller counts the number of copies made with the magazine, and generates a signal that warns the user that the service life of the photosensitive belt has come to an end when the count reaches a preset number of copies. The counter in the machine""s controller is automatically reset upon insertion of a new magazine into the machine. To prevent inadvertent reuse of a spent magazine, a part of the magazine that resets the machine""s counter is broken off when the magazine is first loaded into the machine. Thus, resetting of the counter upon reinsertion of a previously used magazine is prevented. An image forming machine that records the usage of a photosensitive drum, and stops the drum and renders the machine inoperable after a preset number of copies is disclosed in U.S. Pat. No. 4,751,484 issued to Matsumoto et al.
It is desirable to provide a means by which only the appropriate type of cartridge and only appropriately manufactured cartridges may be used with a specific electrostatographic reproducing machine. If an incorrect or improperly manufactured cartridge is inserted into the machine, it may have a detrimental affect on the quality and/or quantity of the documents produced by the machine. Furthermore, an improperly or poorly designed cartridge may detrimentally affect components of the electrostatographic reproducing machine, and may therefore void any warranty on the machine. It is also important to ensure that CRU""s are not used beyond the useful life of the CRU. Using a CRU beyond its useful life may likewise have a detrimental effect on print quality and/or on machine components, possibly voiding any warranty. In some instances, it is desirable to determine whether a machine being operated under a contract or license is being used in accordance with the license.
In order to automatically determine whether a replaceable cartridge or CRU is the correct type of CRU upon insertion of the CRU into the machine, it is known to provided the CRU with a monitoring device commonly referred to as a CRUM (Customer Replaceable Unit Monitor). A CRUM is typically a memory device, such as a ROM, EEPROM, SRAM, or other suitable non-volatile memory device, provided in or on the cartridge. Information identifying the CRU is written on the EEPROM during manufacture of the CRUM. For example, information identifying a CRU as a developer cartridge and identifying the type of carrier, developer, and transfer mechanism contained in the developer cartridge may be written in the memory contained in the CRUM. When a CRU containing such a CRUM is installed in a machine, the machine""s control unit reads the identifying information stored in the CRUM. If the CRU is the wrong type of unit for the machine, then a xe2x80x9cWrong Type of Cartridgexe2x80x9d message is displayed on the machine""s control panel and the machine is deactivated preventing use of the incorrect cartridge. Such a xe2x80x9csecurity CRUMxe2x80x9d system is disclose in U.S. Pat. No. 4,961,088 issued to Gilliland et al.
The maximum number of prints that a CRU is designed, licensed or warranted to produce is also commonly programmed into the CRUM during manufacture of the CRU. When a given cartridge has reached its maximum number of prints, the machine is disabled and a xe2x80x9cChange Cartridgexe2x80x9d message is displayed on the control panel. The spent CRU must be removed and a new CRU must be installed in order to reactivate the machine and continue making prints. Prior to removal of the spent CRU, the machine""s control unit writes data indicating that the CRU has been exhausted into the CRUM""s memory. Should a spent cartridge be reinserted into the machine, the control unit will identify the CRU as a spent CRU upon reading the CRUM. Upon identifying a newly installed CRU as a spent CRU, the control unit disables the machine and displays a xe2x80x9cChange Cartridgexe2x80x9d message on the display panel. Thus, inadvertent reuse of an exhausted CRU is prevented. When remanufacturing a used CRU, the CRUM must be reset or replaced with a new CRUM, before the remanufactured CRU may be used in a electrostatographic machine without being identified as an exhausted cartridge.
In order to prevent resetting and reuse of spent CRU""s beyond their effective lifespan, or beyond the term of a warranty or license, it is known to provide a xe2x80x9ckill zonexe2x80x9d in the memory of a CRUM attached to the CRU. The known kill zones are a fixed area in the CRUM""s memory that, when an attempt to read or access this portion of the memory is made, disables all functionality of the CRUM and causes the machine to stop functioning. For example, one or more of the useful datapoints in the CRUM, such as the datapoint in the CRUM identifying the number of images remaining in the useful life of the cartridge, may be set to zero when an attempt to read or access the kill zone is made. Setting such a useful datapoint to zero will cause the machine to cease operating and display a xe2x80x9cReplace Cartridgexe2x80x9d message on the display panel. In this way a consumer is prevented from employing a CRU that has been improperly remanufactured beyond its useful or warranted life, and the possible detrimental consequences in the form of reduced print quality, possible damage to machine components, and loss of warranty are prevented.
In some instances, consumers have been successful in identifying the location of the fixed kill zone in the previously discussed xe2x80x9csecurity CRUM""s.xe2x80x9d After identifying the location of the fixed kill zone, it is possible to access the non-kill zone portions of the CRUM and reverse engineer the CRUM""s architecture, programming, and identifying information and codes. Upon knowing the approved CRUM""s architecture and identifying information and codes, it is possible to reprogram a spent CRU""s CRUM, and continue to use the spent CRU. When extending the life of a CRU in this manner, a consumer may continue to use a degraded CRU with detrimental effects on the overall operation of the machine in terms of print quality or quantity, possibly voiding any warranties and damaging machine components in the process. In other cases, the consumer may be resetting the CRUM in order to continue operating the machine beyond the terms of a license or contract based on usage or time.
Reissued U.S. Pat. No. Re. 35,751, reissued on Mar. 24, 1998, discloses a monitoring system for replaceable units, such as toner cartridges in an electrophotographic printer, includes on the unit an electronic count memory and an electronic flag memory. The count memory maintains a one-by-one count of prints made with the cartridge. The flag memory includes a series of bits which are alterable from a first state to a second state but not alterable from the second state to the first state. The bits in the flag memory are altered at predetermined intervals as prints are made with the cartridge. The flag memory is used as a check to override unauthorized manipulation of the count memory.
U.S. Pat. No. 5,016,171 discloses a customer billing system for electrostatographic reproducing machines in which a replaceable copy cartridge provides a guaranteed number of copies or prints, each cartridge having an integral copy counter which, on reaching a predetermined copy count, is disabled, rendering the cartridge dead and activating an additional copy counting mechanism for counting a limited number of grace copies that can be made using the dead cartridge, after which further operation of the machine is prevented until a new cartridge is installed.
There is a need in the art for an improved method of preventing unauthorized access of the CRUM, in order to prevent reuse of a spent CRU beyond the effective life of the CRU, or beyond the term of a warranty or license.
The present invention provides a security method for a replaceable component of an electrostatographic reproducing machine. The method includes the following steps. Providing the replaceable component with a memory source having a plurality of addressed floating memory locations. Randomly selecting one of the floating memory locations as a security location. Writing a security code into the security location. Periodically repeating the steps of selecting a security location and writing a security number into the security location.